Apparatus for producing a magnetic return structure

ABSTRACT

A magnetic return structure having a system of control lines for use in a magnetic storer and apparatus for producing the same. A parallel series of conductors are applied to both sides of a foil of insulating material and a keeper composition is applied to the exposed foil and conductors in a manner that eliminates any air gaps therebetween without producing undesirable mechanical disruptions of the system.

United States Patent Stein [54] APPARATUS FOR PRODUCING A MAGNETICRETURN STRUCTURE [72] Inventor: Karl-Ulrich Stein, Munich, Germany [73]Assignee: Siemens Aktiengesellschaft,

and Munich, Germany [22] Filed: Feb. 16, 1971 [21] Appl. No.: 115,676

Related US. Application Data [62 Division of Set. No. 818,884, April 24,1969,

abandoned. I

Berlin 18/47 C, DIG. 33, DlG, 44, DIG. 60, DIG,

' 1 51 Sept. 5, 1972 Primary Examiner-Robert L. Spicer, Jr.Attorney-Carlton Hill et a1.

57 ABSTRACT A magnetic return structure having a system of control linesfor use in a magnetic storer and apparatus for producing the same. Aparallel series of conductors are applied to both sides of a foil ofinsulating material and a. keeper composition is applied to the exposedfoil and conductors in a manner that eliminates any air gapstherebetween without producing undesirable mechanical disruptions of thesystem.

[56] References Cited 2 Claims, 3 Dra UNITED STATES PATENTS Y a1,190,072 7 /1916 Aiken ..18/D1G. 62

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APPARATUS FOR PRODUCING A MAGNETIC RETURN STRUCTURE This application isa divisional of my copending application Ser. No. 818,884, nowabandoned, filed Apr. 24, 1969.

The invention relates to a magnetic return structure and moreparticularly to magnetic return structures for use in magneticstratified storers and means of forming the same.

It is a known practice to utilize ferrite keepers with magnetic returnstructures. The present day practice is to produce the ferrite keepersas independent structures. The keepers are composed of a ferrite powder,an organic bonding agent such as silicon rubber, a solvent such asmethyl-ethyl ketone, a suitable hardener and, in certain instances,additional additives. These keepers are formed into hardened (orsolidified) plateshaped bodies which are incorporated into magneticstorers as magnetic return structures. However, such known keepers havea number of drawbacks, including inability to form an intimaterelationship with magnetic storers of irregular shapes; inability toeliminate air gaps between the keeper and the storer; inability toattain uniform magnetic contact between the keeper and the storer, etc.

It is therefore an important object of the invention to provide amagnetic return structure eliminating the aforesaid drawbacks.

It is another object of the invention to provide an apparatus forforming an improved magnetic return structure.

Yet another object of the invention is to provide a magnetic returnstructure having a particularly high return effect for the magneticfield of a magnetic storage layer.

Other objects, features, and advantages of the invention will becomemore apparent from the following detailed disclosure and drawingsattached hereto, in which certain preferred embodiments of the instantinvention are shown by way of illustration.

These and other objects of the invention are accomplished by applying tothe keeper material (ferrite, binder, solvent, etc.) to a magneticstorage layer while the keeper material is still in a fluid-like orflowable state and allowing the keeper materials to solidify on thestorage layer to form an integrally joined mechanical unit.

As indicated hereinbefore, a system of control lines for magneticstorers is preferably constructed by applying a parallel series ofconductor pieces on a foil (generally only a few pm thick), as on eachof the two sides thereof. Conductor matrices having a series of suchconductor pieces crossing one another are, for example, utilized inmagnetic stratified storers. In order to improve the magnetic return ofsuch magnetic stratified layers to the side of the conductor matrix,keeper structures are utilized. Keepers are plateshaped bodies composedof soft-magnetic materials (i.e., an elastomer impregnated with aferrite powder).

FIGS. 1 and 2 are schematic elevational side views of a system ofcontrol lines having ferrite keepers attached thereto in accordance withthe principles of the invention; and

FIG. 3 is a simplified schematic elevational view of a loaded pressureapparatus in accordance with the prin-- ciples of the invention.

In accordance with the principles of the invention, the air gap for themagnetic return is minimized by applying the keeper material in a fluidstate directly onto the system of control lines and allowing it toharden or set thereon. In this manner, the keeper is intimately bondedwith the foil of insulating material as well as with the series ofstrip-like connector pieces disposed on the foil.

Surprisingly, the manner of applying the keeper material in accordancewith the invention onto a magnetic storage layer does not produce thedistortive mechanical changes in the system. It would normally beexpected that the setting or hardening of an organic bonding agent(i.e., silicon rubber) would materially distort the thin foil of thesystem. Further, when a holding frame is utilized (as disclosed incopending German patent application Ser. No. S 102 858 1X c/2la it mightbe expected that this curing or hardening procedure would cause thestorage layer to break away from the frame through shrinkage or thelike. However, as indicated, no distortive, destructive or disruptivemechanical changes occur.

An advantage of the magnetic return structure of the invention residesin that the solidified keeper structure does not have to be squeezed orpressure-forced against the magnetic storer system. This eliminates thecomplication from the known process of bonding keepers to storers.Further, the magnetic return structure of the invention is particularlyadaptable to irregularly-shaped magnetic storers, such as those havingan uneven surface and/or a curved surface. In other words, a keeper ormagnetic return structure formed in accordance with the invention has anirregular form mating with the particular form (curved or otherwise) ofthe system of control lines (i.e., the magnetic storer system).Additionally, the keepers applied in the manner of the invention do nothave any air gap between the keeper surface and the magnetic storersurface.

In certain instances where an extremely unevenly shaped magnetic storeris encountered, it is nevertheless desirable to apply a force onto thesurface of the fluid-like keeper material until it has set or hardened.Accordingly, the invention also provides a preferred force applyingapparatus for use in such instances. The details of this apparatus willbe described more fully hereinafter.

The magnetic contact achieved by the ferrite keepers applied in themanner of the invention to a magnetic storage layer is extremelyintimate. Air gaps between the magnetic storage layer and such ferritekeepers are reduced to a minimum. As will be appreciated, the fluid-likematerial of the keeper fills up all of the space between the conductorsand the supporting foil. This intimate relationship between the keeperand the storer can readily be demonstrated. A system of conductors isviolently removed from ferrite keepers attached thereto in the manner ofthe invention and it is noted that the surface of the keeper that was incontact with the conductor has been imprinted with the pattern of theconductor series. This is the case even when the conductors are only afew pm thick.

It is particularly advantageous to press the fluid-like keeper materialthroughout its curing or hardening process against the system of controllines with an appropriate means. A vacuum pressure apparatus is aparticularly well suited means to apply such pressure during this stepof the manufacturing process. Such an apparatus is particularlyadaptable to this process since it can exert a uniform pressure on thekeeper material surface and thereby attain an intimate and uniformcontact between the cured keeper and the magnetic storers. Further, avacuum apparatus constructed in accordance with the principles of theinvention has a portion thereof permeable to gases and/or vapors andthereby allow the withdrawal of volatilized solvents and/or diluentsfrom the keeper material. As indicated hereinbefore, the keeper materialis a mixture of ferrite powders, organic binder, solvents, etc. Thepermeability feature of this apparatus allows withdrawal of solventsand/or diluents from the structure during the continual application offorce.

Additional details of the invention are disclosed in the preferredembodiments shown on the drawings and reference is now made to theFigures thereof, wherein like reference numerals refer to like parts.

FIGS. 1 and 2 illustrate a foil 1 of insulating material supporting aconductor 3 (diagrammatically illustrated) on one side thereof andanother conductor 4, in the form of a series of parallel pieces, on theother side of the foil 1. These conductors 3 and 4 define the controllines of the system. A ferrite keeper 2 is attached, in accordance withthe aforesaid procedure, to one or both of the conductors 3 and 4. Itwill be noted that the ferrite composed keeper 2 makes direct andintimate contact with all of the exposed surfaces of the conductors 3and/or 4 and the surface of the foil 1. In this manner, an intimateunseparated attachment between the keeper and the system of controllines is attained.

FIG. 3 illustrates a vacuum pressure apparatus of the invention. Atub-shaped receptacle 11 receives the system of control lines (composedof a foil 1 carrying conductors 3 and 4 thereon) along with thefluid-like material of the ferrite keeper 2. A cover plate 12 isdisposed on top of the keeper material. The plate 12 is gas permeableand may be composed of any suitable gas permeable material, such aspaper. An elastic shim 13 is disposed on top of plate 12. The shim 13 isprovided with a plurality of projections, knobs or other such spacedpieces 13a. The shim 13 lies on the plate 12 in such a manner that ittransfers a maximum amount of uniform pressure onto the cover plate 12and yet provide a substantial area of free space 16 above the plate 12.Gases and/or vapors passing through plate 12 enter free space 16 and areremoved therefrom. Shim 13 can be composed of any elastic material, suchas rubber in the form of, for example, a playing surface of a tabletennis bat. A suction line 14 is mounted to provide a means ofcommunication between the free space 16 and a vacuum source (not shown).An elastic closure plate 15 is disposed on top of the shim 13. Theclosure plate 15 is substantially gas impermeable but is sufficientlyflexible to be responsive to atmospheric pressure. In the arrangementshown, the upper or exposed surface of plate 15 is in direct contactwith ambient atmosphere. The plate 15 is also provided with a circularbead or the like 17 along its peripheral edges to accommodate movementof plate 15 as it responds to atmospheric pressures. A suitable O-ringor the like 18 provides a gas seal between receptacle 11 and cover plate15. Of course, if desired, shim 13 and plate 15 may be combined into asingle pressure plate having a plurality of projections along a surfacethereof.

As is apparent from a consideration of the apparatus, it is openedbetween plate 15 and the upper edge of receptacle 11 by the removal ofseal 18. When the receptacle is open, the shim member 13 and the gaspermeable cover plate 12 are removed and the control line system ofinsulating foils and conductors are placed inside of the receptacle.Then the fluid-like ferrite keeper material 2 is poured on top of thissystem and plate 12, shim 13 and cover plate 15 are reassembled in themanner shown. The edges of the receptacle 11 and plate 15 are thensealed with the O-ring 18 and vacuum is applied via line 14 to evacuateany air from free space 16. As this air is evacuated, atmosphericpressure uniformly forces plate 15 downwardly and exerts a uniformpressure on the shim 13 and the plate 12 causing a uniform compressionof the keeper material. This compression further insures that thefluid-like keeper material expels any gas therein (including vaporizedsolvents, etc.) and uniformly contacts all of the exposed surfaces ofthe foil and conductors. As indicated, any gases within the keepermaterial are able to pass from the keeper material through the gaspermeable plate 12 and out of the apparatus via lines 14. Otherwise,such gases and/or vapors would be entrapped within the keeper materialthereby providing air spaces therein which are undesirable. The vacuumis maintained until the ferrite keeper material hardens or sets and isthen released and the apparatus opened to remove the unitary structureof the system of control lines having a flexible keeper intimatelybonded thereto. The pressure apparatus is reusable any number of timesand the materials composing the apparatus are carefully selected andassembled that it has an extended useful life.

It will be understood that modifications and variations may be effectedwithout departing from the scope of the novel concepts of the presentinvention.

I claim as my invention:

1. An apparatus for the production of a flexible keeper in intimateunseparated attachment with a magnetic storage layer comprising, areceptacle having an open top for receiving a system of control linesand a fluid-like keeper material, a gaspermeable cover plate fittingsaid open top and being superimposed onto the fluid-like keepermaterial, a gas-impermeable pressure plate adapted for mounting abovesaid cover plate and being movable in response to pressure variations,said pressure plate having a plurality of projections extending from asurface thereof, said projections being in pressure-transmitting contactwith said cover plate and defining free space between said cover plateand said pressure plate, a vacuum source, a vapor passage meansproviding communication between said free space and said vacuum source,and a seal means providing a vapors seal between said pressure plate andsaid receptacle whereby vacuum is applied to said free space causingapplication of pressure on said cover plate and fluid-like keepermaterial.

2. The apparatus as defined in claim 1, wherein the pressure plate iscomposed of a shim member having a plurality of projections extendingfrom a surface thereof and a flexible closure member superimposed onsaid shim member and being movable in response to pressure variations.

1. An apparatus for the production of a flexible keeper in intimateunseparated attachment with a magnetic storage layer comprising, areceptacle having an open top for receiving a system of control linesand a fluid-like keeper material, a gaspermeable cover plate fittingsaid open top and being superimposed onto the fluid-like keepermaterial, a gasimpermeable pressure plate adapted for mounting abovesaid cover plate and being movable in response to pressure variations,said pressure plate having a plurality of projections extending from asurface thereof, said projections being in pressure-transmitting contactwith said cover plate and defining free space between said cover plateand said pressure plate, a vacuum source, a vapor passage meansproviding communication between said free space and said vacuum source,and a seal means providing a vapors seal between said pressure plate andsaid receptacle whereby vacuum is applied to said free space causingapplication of pressure on said cover plate and fluid-like keepermaterial.
 2. The apparatus as defined in claim 1, wherein the pressureplate is composed of a shim member having a plurality of projectionsextending from a surface thereof and a flexible closure membersuperimposed on said shim member and being movable in response topressure variations.